Wet suits and dry suits of the type used in aquatic sports, such as wind surfing, board surfing, water skiing and scuba diving typically are fabricated from pieces of foamed neoprene rubber. The suits are comprised of various fabric pieces which are cut into shapes that accommodate the user's anatomy, provide desired elongation, and provide a variety of aesthetic effects. The wet suit pieces are joined together in seams which are either stitched or adhesively bonded, or a combination of both.
When a wet suit is fabricated using a seam stitching technique, the cost of manufacturing the wet suit is reasonable since conventional fabric seaming equipment, such as overlock sewing machines, can be employed. Thus, wet suits having stitched seams are well suited to production sewing and semi-automated fabrication.
Unfortunately, wet suits having overlock-type stitched seams inherently leak water at the seams, which is tolerable for a wet suit, in that it is contemplated that water will enter the wet suit, but is unacceptable for dry suits and for wet suits which are intended for use in cool or cold water locations.
Accordingly, dry suits and wet suits which are designed for use in cold water are formed from pieces of neoprene material which are adhesively bonded together in butt seams so as not to leak water at the seams. Sometimes these suits are also blind stitched to reinforce the seam, but using current adhesive bonding techniques, the glued seams typically have a strength which is at least as great as the foamed neoprene rubber itself.
Adhesively bonding or gluing together two foamed neoprene sheets, however, is a very labor intensive process. Conventional garment-industry fabrication techniques cannot be used because the resiliently compressible neoprene pieces are very difficult to manipulate, and the neoprene requires the application and/or activation of an adhesive bonding material on the edges of the pieces to be joined together.
Wet suits and dry suits are formed from neoprene sheets which have a thickness in the range of about 1 to about 6 millimeters, and the foamed neoprene fabric is both resiliently stretchy and flexible. In some instances, pieces of different thicknesses are bonded together, and often the neoprene will have a nylon fabric facing bonded to one or both sides of the sheet.
Currently, neoprene adhesive bonding is accomplished by applying a neoprene adhesive to the edges of the sheets to be bonded together. Usually the adhesive is applied to a plurality of similarly shaped pieces that are stacked with their edges exposed so that the adhesive can be applied to the edges only. The adhesive is then allowed to dry. A solvent is used to reactivate the adhesive when two pieces are to be seamed together. The pieces to be joined have their edges painted with solvent and then are pressed together by hand. Finally, a pair of pneumatic pliers must be used to positively press or squeeze the edges of the pieces together to insure uniform bonding. The pliers are pushed down into the neoprene foam and the jaws are closed to press the abutting edges of adjacent pieces together. This is repeated along the length of the seam by using a series of longitudinally adjacent pinching and moving steps.
While this technique produces a strong seam, the application of solvent, pressing together of the fabric pieces by hand and pneumatic squeezing of the pieces to ensure bonding all is labor intensive and undesirably costly. Moreover, the pneumatic pliers clamp the pieces together in a manner which appears to result in residual stresses in the seam. Additionally, there are significant health and safety hazards to the wet suit fabricator in connection with the application of solvent and the use of pneumatic pliers.
An example of a stitched and bonded seam construction suitable for use in wet suits or the like is shown in U.S. Pat. No. 4,416,027 to Perla. This seam also includes a reinforcing insert, but as will be apparent, the hand labor required to create such a seam, and therefore the cost of forming the same, is substantial.
Adhesively bonded butt seams have been formed between sheets of plastic and rubber for various other applications. In U.S. Pat. No. 3,615,994 to MacLaine, laminated vinyl-foam resin impregnated sheets, which include a middle foamed layer, are joined together in a butt seam. In the process and apparatus of the MacLaine patent, however, the two edges which are joined at the seam are not compressed proximate the seam by an amount stabilizing the foam, nor are the edges firmly pressed against each other. Instead the sheets are merely held in registration or crowded together by crowding conveyors.
In U.S. Pat. No. 4,231,836 to Ljungqvist, et al. and U.S. Pat. No. 4,867,823 to Pizzorno apparatus and processes for joining together unvulcanized rubber fabric of the type used in automobile tires are disclosed. In both patents, cord strips, which are comprised of fiber or metallic cords that are oriented in a predetermined direction and surrounded by unvulcanized rubber, are joined in edge-to-edge abutting relationship. The apparatus in both patents includes bevelled wheel or roller assemblies which progressively urge the two opposed cord strip pieces toward each other during formation of the seam. The cord strips are held together initially by reason of the inherent stickiness of the unvulcanized rubber, and a separate vulcanization process is required to permanently bond the sheets together.
In both Ljungqvist, et al. and Pizzorno, the sheets being joined are not resilient, but instead are deformable or plastic, unvulcanized rubber sheets (with reinforcing cords or fibers). Since the unvulcanized rubber cord strips are plastic, application of substantial pressure to the cord strips during the joining process will permanently deform the strips. Thus, in Ljungqvist, et al. grooved wheels engage the cords to urge the strips together with minimal rubber deformation. In Pizzorno the rubber sheets are urged together by wide bevelled roller elements which are skewed and have peripheral surfaces oriented parallel to the sticky top and bottom rubber sheet surfaces. Additionally, in Pizzorno a guide wing structure is provided to direct the sheets toward each other. Thus, the wide rollers engage the top, and preferably the bottom, sticky surfaces of the sheets, and urge the sheets together.
While the Ljungqvist, et al. and Pizzorno patents disclose seam forming apparatus which is suitable for moving plastic, sticky, unvulcanized, reinforced rubber cord strips together to form a butt joint, which is subsequently bonded in a separate operation by vulcanization, they do not suggest or attempt to solve the problem of forming a butt seam between resilient, compressible, flexible foamed fabric sheets to which adhesive must be added. The flexible and compressible nature of foamed neoprene rubber, plus the inherent need to employ an adhesive agent, makes the formation of adhesively bonded butt seams very difficult. The neoprene material must be compressed positively together proximate the edges to insure uniform adhesive bonding, and the entire process must be capable of semi-automation so as to be economically comparable to sewn seams such as those made by overlock-type sewing machines. In the Ljungqvist, et al. and Pizzorno patents, for example, the vulcanizing step, which is necessary for a permanent bonded seam, is not integrated with the process of moving the sheets together to form a seam.
Other adhesive activation systems are known in the prior art, but they have largely been applied in lap seams with sheet stock that is not compressible. In U.S. Pat. No. 3,171,415 to Williamson, et al., for example, ultrasonic welding is used to join together the edges of cigarette paper in a lap seam. In U.S. Pat. No. 3,284,257 to Soloff, et al., ultrasonic melting of thermoplastic and thermosetting materials to form a fusion joint is disclosed, and thermally activatable rubber-based adhesives are ultrasonically activated to effect bonding of nylon parts. The patent to Soloff, et al. also discloses bonding together fabrics or textiles in a lapped or accordion arrangement. In U.S. Pat. No. 3,480,492 to Hauser, nylon parts are lapped and bonded together by ultrasonic energy using a nitrocellulose adhesive or epoxy with an exothermic additive. Similarly, in U.S. Pat. No. 3,652,354 to Su, a lap seam is formed between paper sheets soaked with a metal salt complex by using ultrasonic activation, while in U.S. Pat. No. 4,747,894 to Johnston, et al., ultrasonic activation of a starch-based adhesive to form lap seams for corrugated paper board is disclosed.
The suitability of ultrasonic adhesive activation for use in bonding foamed neoprene fabric, however, has not been pursued before, perhaps because of the observed thermal sensitivity of glued neoprene. One commonly encountered problem in connection with adhesively bonded wet suits, for example, is that the bonded seams can fail when exposed to high temperatures. Surfers standing in their wet suits in front of a bonfire on a beach, for example, have reported bonded seam failures. Previous attempts to heat-weld foamed neoprene fabric sheets together have been unsuccessful since the vulcanized neoprene does not have true thermoplastic characteristics. Intense heating merely produces burning and carbonizing of the neoprene material rather than the melting associated with vinyl and other thermoplastics which are directly heat weldable.
While foamed neoprene remains as the predominant material in wet suit and dry suit construction, other materials such as HYPALON (Dupont), KRATON (Shell) and various types of foamed plastics, such as urethane, can be used. For the purpose of brevity, this application primarily will mention neoprene rather than engaging in repeated recitations of alternative materials. The invention disclosed, however, is useful in connection with these alternative materials and in certain cases, such as in the use of HYPALON, the apparatus and process of the present invention can bond either neoprene or HYPALON without modifying the apparatus which is set up for neoprene.
Joining together pieces of neoprene foam in an adhesive butt seam by a continuous semi-automated process, therefore, has presented a substantial challenge. The flexibility and resiliency of the foam makes it difficult to manipulate. The need to use adhesives poses additional manipulation and activation problems and makes automation, with attendant cost reduction, harder to achieve.
Accordingly, it is an object of the present invention to provide an apparatus and method for forming adhesively bonded butt seams between resiliently compressible neoprene sheets which can be adapted to more conventional garment forming techniques with substantial attendant cost savings.
It is another object of the present invention to provide an apparatus and method for forming adhesively bonded seams between neoprene foam sheets which is capable of producing a seam which is very uniform and free of residual stress so as to be at least as strong as the material itself.
Another object of the present invention is to provide a method for forming an adhesively bonded butt seam between resiliently compressible, flexible fabric sheets which can be accomplished in a continuous semi-automated operation.
It is a further object of the present invention to provide an apparatus and method for forming an adhesively bonded, butt seam between resiliently compressible, flexible, fabric pieces in which the manipulation of the pieces and their bonding together is integrated into a single continuous process.
Another object of the present invention is to provide a butt seam formation process suitable for joining neoprene foam pieces together in which seam bonding is achieved by an automated seam clamping process.
Still a further object of the present invention is to provide a butt seam forming apparatus and method in which resiliently compressible fabric sheets can be bonded adhesively together by a manipulating assembly which requires minimal skill to supervise and operate.
Still a further object of the present invention is to provide an apparatus and method for forming adhesively bonded seams between neoprene sheets in which health hazards are reduced and safety is increased.
Another object of the present invention is to provide a method and apparatus which is suitable for adhesively bonded together neoprene sheets of different thicknesses in a butt seam.
Still another object is to provide an adhesively seamed fabric member in which the seam is substantially free of residual stress and bonding is more uniform along the seam.
Still another object of the present invention is to provide an apparatus and method for forming adhesively bonded butt seams between resiliently compressible fabric sheets which produces a durable, high-strength seam, can be accomplished with relatively inexpensive equipment, requiring minimal training and maintenance, and which enables integration of a variety of adhesive activation systems with the material handling equipment.
The apparatus and process of the present invention have other objects and features of advantages which will become apparent from and/or will be set out in more detail in the accompanying drawing and following description of the Best Mode Of Carrying Out The Invention.